12189721 has 4 divisors (see below), whose sum is σ = 12258000. Its totient is φ = 12121444.

The previous prime is 12189703. The next prime is 12189733. The reversal of 12189721 is 12798121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12798121 = 7 ⋅1828303.

It is a cyclic number.

It is not a de Polignac number, because 12189721 - 2¹³ = 12181529 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (12189781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33871 + ... + 34228.

It is an arithmetic number, because the mean of its divisors is an integer number (3064500).

Almost surely, 2^12189721 is an apocalyptic number.

It is an amenable number.

12189721 is a deficient number, since it is larger than the sum of its proper divisors (68279).

12189721 is an equidigital number, since it uses as much as digits as its factorization.

12189721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68278.

The product of its digits is 2016, while the sum is 31.

The square root of 12189721 is about 3491.3780946784. The cubic root of 12189721 is about 230.1430804750.

Subtracting 12189721 from its reverse (12798121), we obtain a square (608400 = 780²).

The spelling of 12189721 in words is "twelve million, one hundred eighty-nine thousand, seven hundred twenty-one".